RESULTS AND DISCUSSION
4.4 Residue Content Analysis
4.4.1 Fourier Transform Infra-Red (FTIR) Spectra ETHYLNE CARBONATE
The peaks between 1000 cm·1 and 600 cm·1 were from the out-of-plane vibrations of methyl or other alkyl constituents on the aromatic group. The dry leaves is mainly constituted of cellulose, hemicellulose and lignin. From the analysis, it can be concluded that the band at 1620 (C=O) represents the hemicellulose. The absorption at 1020 cm·1 represents the cellulose
(p
glycosidic bond) and absorption at 1400 cm·1 and 1600 cm·1 represents lignin.The band at 1630 cm·1 decrease and band at 1020 cm·1 is almost disappeared as retention time of liquefaction increase. This shows that cellulose and hemi cellulose decomposition.
The IR spectrum of the residue at the initial stage (liquefaction at 60 minutes) is similar to that of raw, while the spectra of residues at 120 minutes, 180 minutes and 200 minutes differ from the raw material. Previous studies indicate that the band at about 1400 cm-1 may represent both the overlapping of symmetric carboxyl stretching vibrations from un-ionized carboxylates and C-0-C stretching vibrations from esters.
Thus it is possible that these residues would mainly be derived from lignin.
It has been reported that delignification of dry leaves is more difficult than wood in organic acid cooking because of the condensation reaction of lignin. Under strong acidic conditions, the condensation reaction occurs between carbonium cations at the a- position and electron-rich aromatic ring carbons of lignin compounds, leading to a diphenylmethane structure. The structure formed from guaiacyllignin's is reported to be more persistent in acid catalyzed degradation as compared with that syringyl lignins (Shimada et a! 1997). This mechanism might be interpreted as the liquefaction of dry leaves nit be as thorough.
ETHYLNE GLYCOL
. .. . I
rv'-\ ;·
! \'\. I
~!
I
II I
i,' ,,
~l
! II II
'' I' tI
· - -.. ---~,.,
il10 l.'01 I Ill 1(01 mo
Ill' I
Figure 4. 7 : IR Spectra of (a) Raw Dry Leaves (b) EG liquefaction of dry leaves ( 60 minutes) (c) EG liquefaction of dry leaves ( 120 minutes) (d) EG liquefaction of dry
leaves ( 180 minutes) (e) EG liquefaction of dry leaves (200 minutes)
From Figure 4.7, the intense broad band between 3370 cm-1 and 3410 cm-1 indicates the presence of OH groups in large quantities in dry leaves. It can also be seen that the band at 1620 cm-1 show the residue obtain at 60 minutes still have cellulose and lignin. But the intensity of these bands decreased. Therefore, dry leaves biomass cannot be liquefied completely at reaction 60 minutes.
It can bee seen that the four kinds of residue from different reaction time have the similar functional groups. From the spectral difference of FTIR spectra of these
35
heavy oils and raw material, the absorbance peak appeared on the range 1600-650 cm-1•
It is showed that the aromatic ring start to recombine at this time.
From figure 4.7, those between 930 cm-1 and 684 cm-1 respectively, indicate the presence of the aromatic double bonding. Those at 746 cm·1 and 706 cm-1 respectively are due the presence of 0-substituted benzene ring. These bands in the liquefied dry leaves spectrum indicate the presence of the aromatic lignin based components.
In comparison between FTIR spectrum between ethylene glycol and ethylene carbonate, it can be seen that the band at 1630 cm-1 strongly decrease and band at 1020 cm-1 in ethylene carbonate. This shows that ethylene carbonate give high decomposition compared to ethylene glycoL
From figure 4.6 and 4.7, it can also be seen that there is very strong band at 1400cm·1 that indicated carboxylic acid in ethylene carbonate compare to ethylene glycoL This can conclude that ethylene carbonate give higher yield or conversion from cellulose to carboxylic acid compared to ethylene glycoL
4.5 Mechanism of cellulose solvolysis
-l[.t)j
H()~ '-l_~lc'!Figure 4.8 : Cellulose alcoholysis pathways catalyzed by acid.
._.o
~o
\.,;dr.,; .Kttl <'ll.-1~1 '-~~·r
It is well-known that cellulose, hemicellulose, and lignin are the three mam components of biomass. These components can he alcoholized with acid as a catalyst according to the pathways shown in Figures 4.8. The intermediates include glucose and xylose from cellulose and hemicellulose degradations, denoted as C-OH, and also include the fragments A and B from lignin degradation, designed as L-OH. These intermediates can react further with alcoholic solvents according to the literature review.
When using ethylene glycol a single molecule of polyhydric alcohol can be combined with multi-molecular C-O H. As a result, the molecular weight of products is increased and the formation of heavy oil and residue is promoted with polyhydric alcohols.
In the literature rev1ew, the conversion product of liquefaction ethylene carbonate and ethylene glycol is levulinic acid. Although there is no trace on levulinic acid for this project, the decomposition and degradation of cellulose will be discussed.
We earlier reported that when using EG as a solvolysis reagent, cellulose was degraded and produced a considerable amount of EG glucosides at the early stage of the reaction; then the glucosides decomposed into a large quantity of levulinates. Even in
37
the case of using EC, because EC decomposes into polyalcohols under acidic conditions, glucosides are produced at the early stage of the reaction, after which the glucosides decompose into a levulinic acid structure as in figure 4.9
,· lK~"!llfl' "llif'll 't
I anJ
I
\ ""'~ lll\.(1/,'l(IOIO I
ln~nlubl~
fr:t(non
Fig. 4.9. Mechanism of cellulose degradation and decomposition during the solvolysis reaction, and the solvolyzed product analysis
This project describes a method for analyzing the degraded cellulose in the solvolyzed products. Glucose content was measured by hydrolysis treatment of the liquid product , and was defined as the glucoside content of the solvolyzed products ..
The reaction conditions for the hydrolysis were optimized to give the highest yield of hydrolysis product.